In many signal transmission networks, such as computer networks, data must traverse across different physical layers in traveling from one node to another. The different physical layers may represent physically different signal transmission media, e.g., coaxial cable, twisted pair, optical fibers, etc., or simply signal transmission media of the same type that are electrically isolated from one and another. For example, one node of the network may communicate over coaxial cable using frequency shift keying while another node may communicate over twisted pair wire using differential digital transceivers.
Traditionally, communication between nodes on different physical layers has been accomplished using a gateway. The term gateway is typically used to describe a variety of devices, including bridges and routers, which are used to interconnect similar or dissimilar signal transmission media. When connecting various signal transmission media, gateways must perform functions such as message format conversion, addressed translation, and protocol conversion. Gateways typically employ routing tables, e.g., look up tables, distribution algorithms, and other such software algorithms when performing functions such as determining whether the source and destination nodes reside on different sides of the gateway. Additionally, a separate gateway is required at each signal transmission media interface for providing the desired data transmission.
For networks that use the same protocol across the entire network and having frequent communications between the different physical layers, the processing performed by a gateway may degrade overall network performance. The time it takes for information to travel across physical layer boundaries at a gateway increases due to the "store" and "forward" nature of a gateway wherein data is stored and processed prior to being provided across the physical layer.